A more realistic skeletal mechanism with compact size for n-butanol combustion in diesel engines

Abstract

To accurately predict the combustion and emissions characteristics of a diesel engine fueled with n-butanol/diesel blends, a more realistic compact-sized skeletal mechanism with (149 species and 497 reactions) was developed in this study based on the decoupling method. It was generated by integrating the simplified fuel-related sub-mechanisms of n-butanol and diesel surrogates including n-dodecane, iso-cetane, iso-octane, toluene, and decalin. The same detailed core sub-mechanisms of C2-C3 and H2/CO/C1, in which the formation and oxidation of benzene (A1) and larger polycyclic aromatic hydrocarbon (PAH) up to coronene (A7) of alkanes, aromatics, cycloalkanes and alcohols were used. The PAH formation behavior of individual fuel components in the mechanism were analyzed in detail based on the methods of pathway analysis, rate of production and sensitivity analysis. The mechanism was extensively validated against ignition delay time, laminar flame speed, species profile and three-dimensional engine simulation. The results show that the effects of fuel types on the PAH formation are satisfactorily captured, and the combustion characteristics of n-butanol/diesel blends and each component are reliably reproduced by the current mechanism.

Gas-Phase Synthesis of Coronene through Stepwise Directed Ring Annulation

“…These models incorporate gas-phase reactions forming PAHs up to coronene (C 24 H 12 ) followed by soot nucleation and aggregation via PAH dimerization . While traditional PAH growth processes have focused on the HACA mechanism, , more recent models have incorporated resonance-stabilized free radicals (RSFRs) as well as the hydrogen abstraction–vinylacetylene addition (HAVA) and phenyl addition–dehydrocyclization (PAC) pathways. − ,,− However, even these refinements were not able to replicate the observed fractional abundances of coronene (C 24 H 12 ) in, for example, ethylene flames, with modeled coronene abundances falling short by up to an order of magnitude compared to observed data. , Therefore, the inability to replicate the fractional abundances of coronene (C 24 H 12 ) in combustion flames implies that critical reaction pathways to coronene (C 24 H 12 ) are not properly incorporated in the models. Therefore, an advanced experimental and computational protocol is required to investigate elementary gas-phase reactions yielding coronene (C 24 H 12 ) at elevated temperatures.…”